At least five prominent political prisoners at Rajaeeshahr prison in Iran are on hunger strike to protest being denied the right to visits, phone calls, and temporary leave for medical treatment, RFE/RL's Radio Farda reports.

The prisoners began their hunger strike on April 10 in the prison in Karaj, west of Tehran.

The hunger strikers include labor activist Mansour Osanlou, who heads the Syndicate of Tehran and Suburban Bus Company Workers. Osanlou suffers from a heart condition, but he has not been granted temporary leave from prison since 2007.

The hunger strikers also include Isa Saharkhiz, a journalist and member of the Association for the Defense of Press Freedom. He has been repeatedly denied temporary leave for the past 20 months, despite his poor health.

Another striker, student leader Majid Tavakoli, who has developed respiratory problems during his incarceration, has not been allowed to take leave from prison since his arrest in December 2009. Tavakoli was taken into custody after making a speech during a rally at Amir Kabir University in Tehran. He was sentenced to eight and a half years in prison.

Teachers' union leader Rasoul Bodaghi, detained in September 2009 and sentenced to six years in jail, is also on hunger strike, as is Heshmatollah Tabarzadi, head of Iran's banned opposition Democratic Front, who is serving an eight-year sentence.

Abdolkarim Lahiji, the Paris-based vice president of the International Federation of Human Rights Leagues, told Radio Farda on April 13 that the prisoners want to express their protest against unjust sentences as well as poor prison conditions.

"Even though these prisoners had done nothing against the law -- even the Islamic Republic law -- they were given harsh sentences," Lahiji said.

Another reason for the Rajaeeshahr prisoners' protest is the pressure exerted on their families.

Tabarzadi's son Ali told Radio Farda on April 12 that his family has been repeatedly harassed. He said his mother was summoned by the authorities several times and his sister was threatened on the street.